Insulin-like growth factor binding proteins (IGFBPs) in camels : revelation by western ligand blotting and partial purification of insulin-like growth factor binding protein-3 (IGFBP3)

It's well known that Insulin-like growth factor binding proteins (IGFBPs) are important in somatotrope axis in mammals. They modulate bioactivity of Insulin-like growth factor-I/II. In this study, we identified IGFBPs in blood of camel by Western ligand blotting and we investigated a procedure to purify IGFBP-3 from this species. Three distinct bands are observed. By analogy to that known in mammals, they are identified as insulin-like growht factor binding-3 (IGFBP-3:40-46 kDa), insulin-like growth factor binding proteins-2 (IGFBP-2: 32 kDa) and insulin-like growth factor binding proteins-1 (IGFBP-1: 28 kDa). IGFBP-3 precipitates in 40-60% by ammonium sulfate saturation of serum. Acidification of 40-60% fraction at pH 3.0 is necessary to dissociate IGFBP-3 from tertiary complex (IGFBP-3, acid labile subunit and IGF-I/II). IGFBP-3 is partially purified by anionic ions exchange chromatography at pH 8.5. It forms a clear doublet band.